


blue collar

by Sin_Cognito



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, Established Relationship, M/M, Underfell Sans, collaring, kustard - Freeform
Language: English
Status: Completed
Published: 2017-12-15
Updated: 2017-12-15
Packaged: 2019-02-15 06:05:59
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,959
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13024833
Author URL: https://archiveofourown.org/users/Sin_Cognito/pseuds/Sin_Cognito
Summary: As an expression of what their relationship means to him, Red wants to give Sans a collar, but is afraid of the other's rejection.





	blue collar

**Author's Note:**

> From a kinktober prompt :  
> How about Kustard with collaring. Red giving Sans a collar as an expression of his live and the need to protect him? Maybe Sans would find it strange, so would he accept?

Red kissed Sans, pushing his eager crimson tongue into the other's mouth, effectively muffling a deep moan. He took pleasure in letting Sans think he was in control before his own broad tongue sneaked around Sans' appendage and he began to suck the blue magic. He made sure that he got a taste of every part of Sans' mouth, leaving a trail of red drool and marking his territory. With each brushing of their tongue, Red would lose himself a bit more into an endless well of love for Sans, who also enjoyed himself, if his unrestrained whines were anything to go by. As content as he was with the sloppy make out, Red soon found out that the more they kissed, the more he wanted to ravish Sans, to make him scream his name in pleasure, to make love to him.

Red's practised hands roamed all over his lover's body, finding without problem his most sensitive spots. Red gently lifted Sans' shirt up a little, just enough to reveal his lower-most ribs, and began caressing the bone there. It took Sans no time to become flushed with his signature blue hue. Sans shivered under Red's gruff body, eliciting a spark of pleasure in his magic, that coursed through his entire body. Red switched between caresses and scratches, leaving greyish marks on Sans' body, only to soothe them with the palm of his hands a moment later. Each time his hand would pass on such a mark, Red would groan in ecstasy at the thought of Sans covered in scratches HE made. Red wanted the whole world to know Sans was HIS and his alone. Even if for now, the only marks Sans would let him leave on his body were the ones that could be hidden by his clothes... so that nobody knew what type of relashionship they had...

Seeing the lovely effect his touch had on his lover, Red finally set Sans' mouth free and peppered his slightly smaller body with kisses and nibbles. He slipped his tongue in-between the other's ribs, tasting each and every one of his bones, the taste sweetier than any sinful fruit. His fingers brushed teasingly against the underside of Sans' ribcage, pulling the floating ribs until the bones rattled and Sans' breath hitched. He was so close to his lover's blue soul, he could so easily crush him right here and there, or have the most wonderful soul sex with his mate and give him the orgasm of his life. The choice depended entirely on Red, and boy was that an exhilarating feeling. Sans was willing to let Red do whatever to him, he was so trusting of him, putting his body, his soul, his life on the line because he knew Red would never hurt him. Having grown in his shitty kill or be killed world, been born to a first-class mother fucker, raised alongside a... difficult to say the least little brother, Red had never known how feeling powerful could be. Nor what it meant. He was responsible for Sans, both commanding him and under his ultimate spell at the same time. He didn't think he would ever get tired of this feeling, oh no.

"red... p-please... i need you..."

His lover's moans of pleasure brought him back to reality. Sans was heavily panting before him, sweat beading on his skull and drool dribbling down his chin. His cheeks were flushed a darker blue and glowed in the dark, luring Red's gaze on his lover's face like a moth to a flame. Inhaling a deep breath, Red was happy to detect in the air the telltale smell of ecto magic, probably a sweet pussy for him to fuck. The pussy theory was confirmed once he glanced down to watch Sans' crotch and saw no bulge. Red loved Sans' ecto pussy and couldn't wait to devour him but...

He had sworn he would give it to Sans today.

Ignoring the accumulation of his magic in his groin, Red dove back into Sans' neck, licking each vertebra as if his life depended on it. Sans conciously (or not) bent back his head, leaving his neck wide open for Red to lavish as he pleased. And lavish did Red do. He couldn't for the life of him stop himself from licking this tender neck, going as far as to sinking his sharp fangs into the bone to keep him in place. Sans struggled a bit when he felt the bite, but soon relaxed and even panted for more.

"red... yes... ahn... m-more ! please more ! red ! red !"

Red had the hardest time focusing on what he was doing when Sans chanted his name like this. But he had to stop if he wanted to give Sans his present, and he had delayed the moment long enough as it was. Today ! It had to be today ! He had promised himself it would be today ! So no backing up now Red !

With great difficulties, Red released Sans' neck and pulled back to look him in the eyes. He gently smiled as Sans' frustrated gaze melted into confusion, then worry. He intertwined his fingers with the other's and slowly dropped a chaste kiss on his lips.

"Sans, theres something ive been meaning to give you for a long time now but... i... i mean... i dont know if youll... maybe you wont want it. and i want you to know thats okay too. i love you, youre the love of my life and i... i care about you so so much..."

"relax red its okay, everythings okay." Sans delicately wrapped his arms around Red, pulling him back down so that they were pressed against each other. Sans nuzzled his face into the crook of Red's neck, making the gruff skeleton shiver. "i love you too red, i really do. you can tell me anything you know that right ?"

Red's only answer was to hold his lover even tighter, and they just laid there, on Red's old and dirty mattress, for several minutes, both enjoying the proximity of the other, before Red spoke up again.

"i dont expect you to accept my gift right away, ill give you all the time you need to think about it, but just... think about it okay ? like i said its okay if you dont want it in the end, but please consider... keeping it ?"

"red, why in the world would i not want a gift from you ?"

"please ?"

"... yes red, i promise ill think about it. heh i cant stop thinking about it now..."

The gruff skeleton smiled a little then drew back to kiss Sans once again, whispering a soft "thank you", before going to his closet, where his gift was hidden. He came back to the bed where Sans had sat up and set down a simple black box with a red ribbon. Attached to the ribbon was a little card which read in simple letters "for Sans, I love you -Red".

Sans grabbed the card and smiled at Red, letting him know he was ready to open the box. Red pulled the ribbon and lifted the lid up, revealing to Sans a high blue leather collar.

It happened very fast. So fast that Red would've missed it if he hadn't been staring intensely at Sans. For a fraction of a second, Sans' smile faltered.

Aah.

He didn't like it.

Red didn't know what to say. He didn't want to make things even more awkward than they already were. Yet he had to say something. Because he was the one to put them both in an uncomfortable position, by bringing a gift he knew Sans would probably not want. He knew Sans would not want to wear a collar. He had repeated himself over and over that offering him one would be useless, that he was already lucky to be with Sans in the first place, that he shouldn't think about ruining their relation with a stupid gift, that he-

"red, thank you. i love it"

Red lifted his gaze he didn't remember lowering and saw Sans gently smiling at him, a hand on his own that was holding the damn box. Sans moved forward and kissed Red several times before cupping his head and caressing his cheek.

"i love it. i really do"

Hope was blossoming in Red's chest but he couldn't unhear the 'but' that he was sure was to follow...

"but..."

Well at least, Sans wasn't mad or upset or anything or he would've told Red right away. Red had really insisted on being honest with their feelings when they started dating, explaining to Sans that living in Underfell had made him extremely doubtful of everyone. They had promised each other to tell the truth and to not hide their feelings. Never. And Red knew Sans wouldn't break this promise.

So despite the rejection, Red was glad that Sans still loved him.

"its okay Sans. look, i knew i shouldnt have bought you this, i knew you wouldnt want it. but you know what ? im glad i did. at least now i have an answer. sorry for... erm... breaking the mood."

"no red, i want it. i want to wear your collar"

"you... you do ?" Red was hesitant. He had confidence in being able to read Sans, and he was pretty sure he saw a look of uncertainty on his face earlier when he opened the box. He had assumed it was because Sans didn't want to hurt his feelings by rejecting the gift, but what if it was something else ? What could it be then ?

"i would love to wear your collar red. i want to show everyone i belong to you. i want the whole world to know im YOURS and yours alone. that you chose me out of anyone else to be by your side."

Sans' words resonated in Red's soul, warming him up from the inside. Apparently, Red could fall even more in love with Sans.

"but you know my world" Sans continued. "this type of relationship that we have, that i want to have with you, is as common in your world that it is rare in mine. its still frowned upon in so many places. i dont care about what others will say, but i dont want to have to justify our relationship to anyone. and... i cant even begin to think about what paps will say when i tell him that you hurt me, that i love it when you hurt me. i trust you so much and i know youll never truly hurt me, but i could never blame Papyrus for being protective of his 1HP brother. ooh red, please understand that its in no way shame thats making me reluctant of taking your gift. i told you i want it and i really mean it. but i... i have to think about so many things before accepting it." By the end of his speech, Sans seemed very deflated and tired. Still, he took the collar with a trembling hand and finally said "can i... can i still take it with me while i think about it ?"

Red crushed Sans in a tight hug. Sans wanted his gift ! He liked his gift ! It didn't matter if he wouldn't wear it, he didn't hate it ! Red would be lying if he said he wasn't a bit disappointed in the outcome, but he was just so glad Sans was happy with the gift.

"of course babe !!! i told you, you can take as much time as you need ! and its okay if you dont want it in the end. id rather you didnt wear the collar than wear it unwillingly and be uncomfortable. i love you. with or without a collar."

Sans slowly pushed Red away to be face to face with him and gently smiled before pressing his lips to Red's mouth. Red felt the other's tongue lick across his sharp teeth, asking for an entrance he immediately granted him. Blue and red magic mixed together in a torrid meeting. When the two skeletons finally pulled apart, they were both panting heavily. Sans lifted the collar he was still holding and unclasped the front buckle. He then took Red's hand and placed the collar in it.

"i did say that i have reservations with wearing this collar in my world, but i didnt say anything when we re in yours." Sans' grin turned playful. "so red, would you do me the honor of collaring me ?"

Red was about to do just that when an idea occurred to him. He took Sans' hand and pulled up the sleeve of his blue jacket, revealing the pearly white bones of his wrist. He placed the buckle end of the collar right on the top of Sans' wrist and hold it in place with his thumb, then with his free hand wrapped the collar around the other's wrist. Two loops and the buckle fell perfectly in place with the other end of the collar. Red clasped it together, pulled the sleeve back down to hide it and lifted Sans' arm so that they could admire his work.

"what about this ?"

Sans was silent for a moment, considering the thing. He was wearing the collar, yet no one would be able to notice it under his sleeve, even less with his hands buried in his pockets. He would be able to wear the collar each and every day, in the middle of a crowd, and nobody would be able to tell. When he would come to Underfell, he would wear it around his neck, and as soon as he would go back to his own universe, he would just have to put it around his wrist and Jerry's your uncle !

"fuck red youre a genius."

"i know."

 

* * *

 

 

Sans was gently caressing Red's naked ribcage.

After Red had wrapped the collar around Sans' wrist, the two lovers hadn't wasted time in getting back to where their... activity had stopped. Several climax after and they were now hugging each other on the dirty mattress, lower regions still sticky with the remaining fluids of their love making. Naturally, neither of the two wanted to get up to clean the undeniable mess.

So they were both enjoying each other's company in contented silence when Red spoke up.

"hum... i have something else."

"red im way too tired to go another round." Sans chuckled, though it sparked his curiosity. He just hoped it wasn't a leash to go with the collar, because there was no way he would agree to be on a leash in either his or Red's world.

"when i bought your collar, i considered buying something for me as well. something to go with your collar you know ?"

_-not a leash, not a leash, not a leash-_

"so i bought a matching collar. for me."

Sans' eyes opened wide.

"what ? but... you already have a collar."

Even before they were together, Red had explained he had been wearing Boss' collar for the past maybe 10 years or so to warn other monsters not to fuck with Boss' property. That if they were to lay a single paw, claw, fin or whatever on Red, Boss would come to destroy them so much that not a single speck of dust would be left of them. Red's brother's reputation as the most violent member of the royal guard had done wonders to the 1HP monster's security, but everyone knew that without Boss' collar, Red was as good as dust. No, Sans thought, he wouldn't risk Red's life just for wearing a matching collar to his own.

Besides, he knew what the red collar meant to Red. That it wasn't just an edgy item to keep Red safe. It was the one and only mark of affection Boss had ever given Red.

"red, i dont like the idea of you not wearing your brothers collar. its too dangerous for you. and you know that theres no way monsters here will be intimidated when they see you with a collar with my magic signature on it. as if theyd be afraid of me."

"pff thanks but im no suicidal" the gruff skeleton laughed. Phew. Red wasn't stupid enough to take off the symbol of his brother's protection. "im thinking about something else. a way for me to wear it without having to remove Boss' collar."

"like for me you mean ? wrap it around your wrist ?" Sans questioned while wondering if it could work.

"mmmh not really... in fact ive already found a way. and i am wearing my matching collar right now."

The surprise must've shown on Sans' face because Red turned on his side so he was face to face with Sans. He lifted his hand up to the red collar and unclasped the front buckle. The collar fell from Red's sturdy shoulders and revealed a much thinner collar that was the very same blue as Sans' one. It was fitting tightly around Red's neck, yet it didn't seem to hinder the movement of his head. And most importantly, it was truly invisible when underneath the bigger red collar.

"i want to wear this collar as a symbol of my love for you. i wont ever take it off, but when in my universe ill have to wear Boss' collar on top of it. i know you understand why. and when i come visit you in your universe, well... ill take the red collar off... and proudly display my blue collar. the same goes for when we'll be alone like now."

Sans was so filled with emotion he didn't trust his voice so he just hugged tighter his one true love.

"im yours just as much as your mine."

**Author's Note:**

> I'm not part of the BDSM lifestyle so to avoid offending people I asked someone who is part of it for advice. Feel free to come talk to me on tumblr if you've spotted something wrong with how I depicted their relationship. My goal here is to share what I've learnt through my researches about the subject, even if I'm not involved in a BDSM relationship myself (though I really want to be).  
> https://sin-cognito.tumblr.com/


End file.
